I've read a ton of various posts about different aspects of LED lamps, strips, comparisons with fluorescent and incandescent lamps, and I decided that I want to install LED strips to light my room. Strips seem to give off the most natural light of all options, are relatively cheap, come in different colors, can have variable lengths and don't take up much space. But there were several aspects which I'm still confused about.

  • Brightness of each strip is different. I'm planning on using a dimmer anyway, but how do I find and measure maximum desirable brightness level for my room? (my current lighting situation is a mess, so I wouldn't try and match it)

  • Uneven light comes off of an unfiltered LED strip, because diodes are placed in a dotted line. Common recommendation is to use light diffusing filter, which scatters the light enough to make it even. Although these filters take away up to ~30% of total brightness (measured with luxometer). What kind of filter should I get?

  • Positioning seems to be very important. People say placing a strip parallel to a surface can absorb up to a third of total brightness. At what angle should I install a strip in different locations?

  • Light spectrum is often unusual, especially with cheap low quality strips. I still don't know how to tell HQ from LQ LEDs. My local store doesn't have many and they're all generic types.

  • Dimmers have to be of certain types to work with LED strips. Very often I see recommendation to get dimmer amplifiers. Aren't there any dimmers that work fine without additional expenses?

  • "White" color is a vague definition. How do I easily select the color temperature that's right for me? Do I have to buy different strips and compare them on site? Or is there an easier way?

  • SMD ~~~ codes are still a mystery to me. Some say it only determines the dimensions of a single LED unit and its relative socket on a conductor strip, others say it also affects light spectrum and overall strip lifespan. Does it matter?

  • Noise from power supplies seems to be a common problem indoors. People recommend to use waterproof models, which are somewhat airtight, and it helps reduce the noise. Others recommend to install regular power supplies in a waterproofed power box. The former appears to be more expensive, and the latter takes up more space. Radicals recommend placing power supplies in a far location, connecting to the strips with long wires, but that creates some safety concerns. How do I make sure there is no noise and it's still safe?

  • IP class determines how much protection LED strip has. Does it affect installation, use and light in any way?

That's a lot to consider about lighting. If I missed something important, please let me know.


5 Answers 5


It's easier than it sounds. You just have to think rightly about the various issues.


is measured in lumens. In a closed small space like a room, this works out to be a fairly absolute unit. 1000 lumens is about the same amount of light, whether it's coming from an Edison bulb or a LED strip. That's not the whole picture, but the considerations are fairly obvious, e.g. is the light near your workspace, is it "bounce light" etc.

(on the other hand, when dealing with light traveling a long distance, e.g. a headlight, then you get into a lot of complicated geometry and optics and units like candela. You don't need to deal with that in a closed space like a room.)

Light spectrum and "Whiteness"

Color Temperature describes the color of the light. 2700K is a traditional yellowish incandescent. 3000K is halogen. 4100K is traditional fluorescent. 5000K is modern fluorescent, and it gets bluer from there. Higher numbers seem brighter and are great for task lighting, say, in your workshop... but for aesthetic reasons, you will want a warmer (yellower, lower) color temp in the more "homey" parts of your home. Seriously. 5000K sounds great in the showroom, but you'll end up tearing it out.

enter image description here

Next is CRI, or Color Rendering Index. That is the thing that really bothers people about bad lighting - remember those very yellow street lights, which had a CRI of about 15? 100 CRI is perfect. 80 CRI is readily available, and >90 CRI is available with a bit of hunting.

enter image description here

LED production is a bit of a dice roll. Manufacturers never quite know how a batch will come out, so they test and grade (bin, verb) by color temp and CRI. You'll see the bins discussed on LED datasheets. They get top dollar for the most desirable color temps and CRI's. The least desirable bins get dumped to the LED strip makers you find on eBay. If they don't state CRI, it's because they're taking the leftovers and don't know what they're going to get.

Lumens, color temperature and CRI are used for all lamps of all kinds. Nowadays you should be using lumens, not "watts", to pick bulb brightness. "60 watt equivalent" is marketing bull; lumens are an accurate number.

Uneven light and Positioning

LED strips have emitters at a certain spacing. This is completely obvious the moment you turn one on. LEDs emit a great deal of light from a tiny spot, which can be disturbing. Obviously, you have to deal with that in your design. Cove lights or other bounce lighting are perfect for diffusing LED light.

It really helps that unlike any other bulb, LEDs emit light in a cone of about 140 degrees. So you can aim the light where you want it, and don't waste light where you don't.

SMD codes

tell you what kind of power the LEDs require. From here on out, I'm going to talk about a 12V strip (which by design has 3 LEDs in series). A 24V strip has 6 LEDs in series, so current will be 50% typically.

A 3528 device has 1 channel or color, with 2 wires total, + and -. On a 12V strip, 300 LEDs draw 2 amps. That's the handy math to remember. I've tried doing the math other ways, but this is the simplest.

Suppose you have a half-density, 150 LED per 5 metre strip. Half the LEDS = half the amps, 1A. A double-density 600-LED strip takes 4A. Etc. You cut a strip to half length, half the amps.

Suppose you have a standard 5-metre, 600-LED strip (that's double the 300, so 4A per 5 metres). But you are using 2 metres of it, or 2/5 of the strip. That's 4A * 2/5 = 1.6 amps.

A 5050 device has 3 channels. Often 3 different colors, but sometimes 3 of the same color, typically a white. 300 LEDs draw 2 amps per channel, 3 channels. The same multiplying and dividing rules apply.

For instance, the common 300-LED RGB strip with 5050s. It has 3 channels - R G B. How much power does it take? 2 amps per channel, 6 amps whole-strip. Easy peasy. Now, what about the return/common wire? Oh, that takes the full 6 amps.

For instance, suppose we have a RGBW combo strip that has 300 5050's. Except half of them, 150, are RGB LEDs. How many amps do those take? Correct, there are 150 of them, so they take 1 amp per channel, or 3 amps in combo. Then it also has 150 WWW LEDs (white-white-white), and all 3 of those channels are wired together. How much current do those take? Same math, but all 3 wired together, so it takes 3 amps for that channel. See how that worked out? The common return is a whopping 6 amps.

What do those numbers mean? A 5050 LED package is 5.0mm x 5.0mm. A 3528 is 3.5mm x 2.8mm. That's all.


An LED-strip "controller" is simply an LED-strip dimmer that dims R, G and B channels independently, yielding millions of colors. You cannot use any random dimmer with LED strips. ** Dimming and color-blending are done by PWM (pulse-width modulation). *** The LED turns on and off very rapidly - thousands of times a second, far too fast to see. The percentage of "on" vs "off" decides how bright it is. (this is called duty cycle).

Since PWM is hard on/off, it's digital and it can be copied accurately. That's what an amplifier does. It pulses power to its own LEDs, but it uses the controller/dimmer as a pilot signal. As such, it pulses the same, and yields the same brightness. So if you have an 8A controller, you can use that to drive a 6A LED strip, and also an amplifier driving another 12A of LED strip. This all works.

enter image description here

A possible amplifier configuration, here with RGBW strips which have 4 channels instead of 3. Black is common.

Noise from power supplies and Waterproof

This is not a common problem, and it's easy to make power supplies silent. If you can hear your power supply, get a better power supply. Waterproofness has nothing to do with loudness. Some power supplies have fans, obviously those are not silent. Nothing about noise makes it any safer.

If you use LEDs indoors, IP ratings are irrelevant, except water-resistant LEDs are easier to dust. However the water shielding will yellow or get cloudy long before the LED wears out, and will be the limiting factor in LED life. Outdoors, on the eBay cheapies, don't expect long life out of the waterproof coatings, maybe a year.

** In fact, it is a sad cliche where consumers want certain functionality, so they randomly pick products off the shelf at the big-box store, and expect them to work together even though they are not listed to work together. Don't do that. Anytime products need to work together (you know, like a lamp and a dimmer), make sure they are designed to work together.

*** You must not use PWM to "dim" consumer-packaged LED products such as screw-in bulb replacements, driving lights etc. because they have their own internal smart power supply. That power supply will defeat the dimming, treating it as a power quality problem and compensating by drawing more power to keep its light on at full power. This can overload things. So, for instance, if you have your dimming LED strip system, and you see some nice 12V IKEA spot lights you'd like to add to the system, ask or study a teardown to see if that lamp is compatible with PWM dimming. (i.e. it contains only LED emitters and resistors).

  • Question about your amplifier setup, could you split a single amp output to power 2 strips in parallel? I have 2 5 meter strips that use 23 watts that I want to control with a single controller but the PS and controller that came with each only outputs 2A.
    – Preston S
    Commented Mar 1, 2017 at 4:32
  • Sure, if your power supply and amplifier is big enough to handle max rated current. (PWM dimming does apply max rated current during the "on" part of the pulse). All LED strips are paralleled anyway, so forking amplifier output to drive 2 strips is simply doing more of that. Commented Mar 1, 2017 at 16:19

Not a complete answer, but here's some more info.


While there are ways to calculate this that aren't that complicated, it requires knowing many coefficients that are not readily available, so ends up being an educated guess at best. You can do just as well totaling your current lighting's lumen output, then adjusting for changes in fixture styles. (I consider even a simple LED strip a "fixture" for the sake of this discussion) It's a starting point. If you use proper task lighting, there's a lot of room for variance in total levels.

Uneven light

You do not want to see the actual LED elements, it's really annoying. Besides diffusers, indirect lighting techniques work well, though require more lumens due to losses through reflection.


I'm not sure what the issue is with parallel surfaces. The efficiency is mostly inherent in the fixture's ability to direct light where it's needed. The mounting surface has little to do with this, you need to direct the light where it's needed.

White Light

The "whiteness" is measured in degrees Kelvin. The temperature a black body must be heated to emit the same color of light. Standard daylight is often taken to be 6500K, anywhere in the 5000-7000 range is close enough for most tasks. You eyes adapt quickly to small variances. In residential settings, daylight is considered too harsh because we are so accustomed to incandescent lighting, so most home lighting is produced to output more in the 2000-3000K range to mimic the orange incandescent lighting.


How audible the noise is varies by manufacture and environment, as well as personal temperament. I don't think noise data is readily available. Testing in a noisy store will not yield any useful data, other than if you can hear it from a few feet away it is too loud. Noise can be attenuated by placing it in an enclosure, but keep in mind power supplies generate heat that has to be removed by ventilation, you cannot seal it into a sound proof box.

Try to place power supplies as far from your pillow as possible, trying to sleep is when it will be most bothersome. Placing it lower so there is likely to be more furnishings obstructing a direct path will help, as well as being surrounded by soft materials that do not reflect sound as well.


It's not clear to me by your statement that strips "come in different colours" if you were planning on buying an RGB array or not.

My suggest is spend the tiny bit more (it's usually only an extra 10-20%) to get an RGB array and you can reduce a lot of these concerns.


An RGB array has the advantage of being able to be set to whatever spectrum you prefer. For me, this varies from room to room, and tends to also be dictated by the color of the walls of the room I'm using them in.


The cheaper RGB arrays are actually better here as the individual diodes will be separated and thus when creating white light will need to diffuse into each other, so you won't get single pinpoints of light.

Further, if you are the DIY type, don't spend any extra money on a diffuser; you can just slide a white soda straw over the strips and it will work just as well if you find you need one.


Once again, your desired luminosity is likely going to be slightly dependent on the spectrum you choose. The nice thing about LED strips is that it's easy to just add another one if your find your room is too dark.


I wouldn't worry about this in any context, the nice thing about LEDs, is like traditional incandescents, one should be able to just add an extension cord with built in voltage regulator after the fact if they feel the need to dim.

However RGB offers a small advantage here as well as preconceived dimness with change if one sifts from white to say red.

Uneven light / lighting position

The key here is to ensure you have adequate lengths of wire between each strip if you plan to string them in series. This way, you can freely play with the position and angles until you figure out what works best with your room layout.


Shouldn't be a problem if you choose a solid state transformer (which generally comes with cheaper / lower powered strips).


Unless you have a very specific application in mind, you likely don't care about these.

I've seen SMD also relate to the number of actual LEDs in the light.

LEDs are quite durable, so unless you plan on using them in a moist or rugged environment, there's no real reason to care about IP.


This is a big deal with RGB set-ups; and where I'd recommend doing most of your background research

The controller will have to be compatible with your set-up (do you use 4 wires or 6?). You can opt for it to be remotely controlled. And often they come with pre-set functions, and you must ask yourself how much control you want outside those functions.

I personally got some from IKEA, but now notice that the pre programmed fade doesn’t actually fade though all colors evenly, and I have no way to program a new one unless I buy a new controller -- this drives me nuts.


Brightness: Professional lighting Designers use lumens per metre to calculate the amount of light that is needed for the room using software on a computer in which to do this. So measuring this is unlikely but as a guide 5w per metre (around 300lm) is for highlighting, 10w is bright enough to use as work light (around 600lm).

Uneven light: You do not want to see the LED strips themselves so hiding them away and using the reflection is one way of doing this, or you could use a optic lens which will disperse the light at a wider angle.

Positioning: As LEDs can be placed almost anywhere, placing them in the areas you need the light would be most effective for you.

Light Spectrum: If you take a look at this blog post: what is the difference between instyle led strip and standard led tape, it clearly shows the difference between the quality between the different tapes. The HQ has a premium coating over the tape which strengthens giving better protection and stops short circuiting, as well as using higher quality LED chips and resistors. There are high quality branded LED chips (e.g. Epistar) and then there are also cheaper copies which look identical. I have noticed that the copies are only 80% of the brightness and last up to about two years compared to up to 15 years on the branded chips. The best way to tell is by the price and the reputation of the LED supplier.

Dimmers: The main ways of dimming LED’s are using a TRIAC, Dali or a 0-10v protocol, it is however possible to get a variable driver which can be connected to a standard rotary wall dimmer which will allow you to dim the LEDs using your existing house wiring.

White: LED strips come in a wide range of colours which are labeled with the colour temperature from the Kelvin scale. Using this scale will allow you to decide on the colour you want without having to compare the different colours together. Pure White is found at the 6000k part of the scale and Warm White can be found at the other end of the scale at 2700k.

SMD: The 3528 chip only has one light source, the 5050 has 3 light source’s within the chip making it 3 times brighter than the 3528. The 5050 chip was originally designed for the RGB chips so that it could use 3 different colours, but can now be used to display 3 of the same colour source. This also makes the 5050 chip bigger meaning it has to be attached to a bigger tape. As for lifespan they both have 50,000 hours. If you take a look at this blog post: LED Tape brightness range it shows different types of tape you can get and what the LED chips look like, so you can get an idea of what you will be dealing with.

Noise from power supplies: The 30w, 60w, 100w power supplies be it an internal or IP rated but do not make a noise, depending from which manufacturer you get them from. The higher powered 200w and 320w have a fan installed to help reduce the heat that is built up and do make a noise. So it depends on how many metres of LED Tape you will be using to decide on which power supply you should be using and how many you need.

IP: IP stands for Ingress Protection which gives a rating of how resistant it is to dust and fluid.The first part of the number is the resistance to dust and the second part of the number is the resistance to liquid. If you are looking at getting a protective sleeve for your LED Tape, you can purchase it in an IP67 rating which means it will protect it from dust and any liquid that may come into contact with it, as well as being able to be submerged in water up to 1 metre for 30 minutes. This sleeve which is usually a plastic heat shrink cover will not affect installation, as for the colour adding the heat shrink can make the colour of the LED a little darker, but if you are buying it in IP this will not be a problem as it will already have been measured.


I'll be updating my own answer with information I find.

SMD type

Basically, SMD number is the dimensions of the diode in tenths of millimeters. So SMD 5050 = 5.0mm x 5.0mm square diode. The larger the area of the diode, the more even light and heat distribution is.

IP rating

Common IP ratings are numbers like 20, 23, 33, 54, 65, 67, 68. This page has a nice table with corresponding protection levels. The first number signifies the level of protection against solid objects, and the second − liquids. So, IP 23 is not safe enough to use in bathroom, where shower can get to it, but IP 65 and higher is okay.

Light spectrum

Not really about light spectrum, but close enough, is CRI, Color Rendition Index. It determines how realistically colored the objects look in the light of a light source. Most realistically being rendered, are objects lit with incandescent and halogen lamps (100), and light emitting diodes vary around 80. My sources (forums and blog posts) note that although LED strips don't give off perfect light, even distribution of strips and the use of light diffusion filters helps improve the situation significantly.

  • SMD is the electronic chip industry's acronym for surface mount device which means the packaging does not have leads to solder into a hole, but that it is expected to be wave soldered directly to conductive pads on the printed circuit board. SMD packaging is smaller and less expensive, especially because they are easier for automated assembly equipment to handle. LED light consumers probably don't care about whether a fixture has SMDs or not.
    – wallyk
    Commented Jan 31, 2014 at 20:15
  • To clarify, diffusers will not change the CRI, they make the illumination more evenly distributed. CRI 80 is adequate for most situations. For tasks requiring exacting color rendition, such as graphic arts work, only 100 will really suffice, though 95 isn't too bad. One can use specific task lighting for this, general illumination by LED will not be a problem with proper task lighting.
    – bcworkz
    Commented Jan 31, 2014 at 20:23
  • @wallyk for some reason I'm seeing SMD as a sorting and filtering parameter on electronics web-stores. Commented Feb 6, 2014 at 18:43
  • @user1306322: Yes of course. When you are buying LED parts, the packaging (leads, no leads, wirewrap, etc.) is quite important when figuring out which type to purchase.
    – wallyk
    Commented Feb 6, 2014 at 19:20
  • @wallyk it was in use-ready LED strip section. That's why I thought it mattered. Commented Feb 6, 2014 at 19:28

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